Discrepancy detection and vulnerability to misleading postevent information

When people are exposed to misleading details after a witnessed event, they often claim that they saw the misleading details as part of the event. We refer to this as themisinformation effect. In four experiments, involving 570 subjects, we explored the role that discrepancy detection plays in the misinformation effect. Experiment 1 showed that subjects who naturally read a post-event narrative more slowly were more resistant to the effects of misleading information contained in the narrative. In Experiment 2, subjects who naturally read more slowly were more likely to detect a discrepancy between what they were reading and what was stored in their memory. In Experiment 3, subjects who were instructed to read slowly were more likely to detect a discrepancy than were those who were instructed to read quickly. In Experiment 4, subjects who were instructed to read slowly were more resistant to misleading postevent information. Taken together, these results suggest that longer reading times are associated with a greater scrutiny of postevent information. This leads to an increased likelihood that discrepancies will be detected and that the misinformation will be resisted.     

Misinformation effects in eyewitness memory: the presence and absence of memory impairment as a function of warning and misinformation accessibility

The authors report 5 experiments investigating how exposure to misleading postevent information affects people's ability to remember details from a witnessed event. In each experiment the authors tested memory using the modified opposition test, which was designed to isolate retrieval-blocking effects. The findings indicate that retrieval blocking occurs regardless of whether the misleading information is presented before or after the witnessed event. In addition, when people are warned immediately about the presence of misleading information, they can counteract retrieval-blocking effects but only if the misinformation is relatively low in accessibility. The authors discuss the findings in terms of the retrieval-blocking hypothesis and a hypothetical suppression mechanism that can counteract retrieval-blocking effects in some circumstances.     

Memory impairment and source misattribution in postevent misinformation experiments with short retention intervals

The four experiments reported here provide evidence that (1) misleading postevent suggestions can impair memory for details in a witnessed event and (2) subjects sometimes remember sug-gested details as things seen in the event itself. All four experiments used recall tests in which subjects were warned of the possibility that the postevent information included misleading sug-gestions and were instructed to report both what they witnessed in the event and what was men-tioned in the postevent narrative. Recall of event details was poorer on misled items than on control items, and subjects sometimes misidentified the sources of their recollections. Our re-sults suggest that these findings are not due to guessing or response biases, but rather reflect genuine memory impairment and source monitoring confusions.     

Influences of misleading postevent information: misinformation interference and acceptance

Because of the biasing nature of retrieval tests, evidence that the introduction of misleading postevent information will impair the memory for an original event has recently been in dispute. In two experiments, a retrieval test sensitive to both biasing effects of misinformation (misinformation acceptance) and influences of the misinformation on memory (misinformation interference) was used. Both experiments demonstrated misinformation acceptance, and one of the experiments suggested that misinformation interferes with the ability to remember the original event. Two misinformation interference hypotheses are evaluated; they suggest that the misinformation may have either impaired memory or led to confusion regarding what had occurred during the event.     

Sleep Increases Susceptibility to the Misinformation Effect

When individuals witness an event and are exposed to misleading postevent information, they often incorporate the misleading information into their memory for the original event, a phenomenon known as the misinformation effect. The present study examined the role of sleep in the misinformation effect. Participants (N = 177) witnessed two events; were exposed to misleading postevent information immediately, 12 hours later the same day, 12 hours later the next day, or 24 hours later; and then took a recognition test. All groups demonstrated the misinformation effect, and this effect was larger in groups with an overnight retention interval. Signal detection analyses revealed that sleep decreased sensitivity. These results suggest that sleep increases susceptibility to the misinformation effect, which may occur because sleep results in gist‐based representations of original events or because sleep improves learning of postevent information. Implications for interviewing eyewitnesses are discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Memory strength affects reporting of misinformation

A model of long-term retention was used to examine whether and how the strength of original information (differences in learning and testing time) and the strength of misleading information (differences in timing and frequency) influence 3- to 5-year-olds' memory for an event. In three experiments, preschoolers viewed a slide presentation depicting an event, some of them were asked misleading questions, and memory for event details was tested. There was little evidence of memory impairment, but exposure to misleading information encouraged reporting of this information. Differences in learning influenced reporting in that children exposed to the event once reported more misled details than those who saw the event multiple times. Furthermore, preschoolers who saw the event once were just as susceptible to misleading information whether exposed to misinformation once or three times; however, preschoolers who had seen the event multiple times were susceptible only to repeated presentations of misinformation. Given that the reporting of misinformation is determined by the degree of integrity of both the original and misleading information, it is important to control for differences in trace strength for both types of information in future research.     

Correcting the misinformation effect

Decades of memory research have demonstrated a dire need for effective methods of correcting misinformation, particularly once it has been encoded. However, much of this research has exposed participants to misinformation first then provided a correction, and used indirect memory questions. Using a misinformation effect (ME) paradigm, in which participants' memory is distorted by misleading postevent information, we examine whether corrections can combat memory distortion on direct memory tests. Experiment 1 showed corrections greatly reduced the ME. Experiment 2 replicated this finding with a longer lag time (3 min) between exposure to misinformation and its correction, except for participants that read only the misinformation and its correction. Experiment 3 ruled out the possibility that participants reported the most recent information they read, suggesting participants evaluate the correction's veracity. Finally, a meta‐analysis of the three experiments reiterates that corrections may be effective in combating misinformation.     

Misleading postevent information: Testing parameterized models of integration in memory

A classic series of experiments by Loftus, Miller and Burns (1978) showed that a person's recollection of an event can be changed by misleading postevent information. Several hypotheses accounting for this effect have been proposed. Loftus' hypothesis of destructive updating claims that the original memory is destroyed by the postevent information. The coexistence hypothesis asserts that the older memory survives but is rendered inaccessible through a mechanism of inhibition or suppression. The non-conflict hypothesis simply accounts for the effect by claiming that subjects can only be misled if they did not encode or if they forgot the original event. These three hypotheses were modelled with the help of all-or-none probabilistic event trees. An experiment was conducted in order to test the three models and to assess parameter values. The experiment followed the classic Loftus paradigm. We suggested to some subjects that they had seen a stopsign, whereas in fact they had seen a traffic light. The misleading postevent information resulted in poorer reproduction of traffic light. Later, all subjects were asked whether they could remember the color of the traffic light, even if they believed they had seen a stopsign. The results showed that subjects who received the misleading post-event information were at least as good at recalling the color of the traffic light as subjects who did not receive misleading information. The no-conflict model accounts well for the obtained results, although the two other, less parsimonious, models cannot be entirely rejected.     

Testing potentiates new learning in the misinformation paradigm

Retrieval enhanced suggestibility (RES) is the finding that the misinformation effect is exacerbated when a test precedes misleading postevent information (Chan, Thomas, & Bulevich Psychological Science 20: 66–73, 2009). In the present study, we tested three hypotheses relevant to RES. First, we examined whether retrieval of critical details was necessary for the RES effect. Second, we examined whether initial testing influenced the allocation of attention to critical details during postevent information processing. Finally, we examined whether RES resulted in impaired access to the originally learned information. We compared three groups of participants in three experiments: an identical-test group, a related-test group, and a standard misinformation group. Both testing groups were tested on the original event before the introduction of misinformation; however, the identical-test group took the same test before and after the misinformation, whereas the related-test group took different tests before and after misinformation. We found that testing before misleading postevent information affected attention allocation to details in the postevent narrative. Furthermore, the RES effect did not accompany reduced accessibility to the original information, as measured by a modified–modified free recall test. These data have implications for how testing may potentiate new learning.     

Relative - not absolute - judgments of credibility affect susceptibility to misinformation conveyed during discussion

People remember different details about the same events, and when they discuss events they exchange new – and misleading – information. Discussion can change memory, especially when the source of new information is highly credible. But we do not know whether the effects of credibility are based on absolute judgments – judging a source's credibility independently from our own credibility – or relative judgments – judging a source's credibility only in relation to our own credibility. We addressed this question by manipulating subjects' expectations, leading them to believe that they either had the same, higher or lower “visual acuity” than their partner while they watched a movie together. To create ample opportunities for the pairs to mention misleading details to one another, each member unknowingly saw a different version of the movie. The pairs then discussed some of the critical differences, but not others. Later, everyone took an independent recognition test. Subjects' susceptibility to misinformation depended on their own credibility relative to their partner's, supporting the idea that susceptibility to misinformation depends on relative differences in credibility.     

The role of commitment in producing misinformation effects in eyewitness memory

We conducted three experiments exploring conditions in which misleading postevent information interferes with people’s ability to remember details about an event they witnessed. The key condition included in each experiment was the misled-plus-commit condition. After viewing slides depicting a crime, subjects in this condition read a narrative that contained misinformation. Following the narrative, they completed an interpolated recognition test that induced them to select the misinformation. Assessment of memory for the slides using a final, modified recognition test indicated that performance in the misled-plus-commit condition was most frequently near chance, whereas performance in the control condition was far above chance. This result was obtained on four separate occasions and indicates that prior retrieval of misinformation impairs memory. Another important finding was that the deleterious effect of passively reading about misinformation in a narrative is not as great as the effect of reading about it and then selecting it on an interpolated test. Actively retrieving misinformation seems to cause particularly deleterious effects. Our conclusion is that the findings are compatible with the retrieval blocking hypothesis, which assumes that repeated retrieval of misinformation blocks access to the witnessed information.     

Similarity of encoding context does not influence resistance to memory impairment following misinformation

Several recent studies have shown that exposure to verbal misleading post-event information does not impair subjects' ability to retrieve originally seen details. Two experiments were conducted to test the hypothesis that subjects would be more susceptible to memory impairment if the original and misleading information were presented in similar contextual formats. The results showed that misleading information did not lead to memory impairment when both original and misleading information were presented in the context of slides (Experiment 1) or when both original and misleading information were presented in the context of narratives (Experiment 2). Furthermore, resistance to memory impairment was observed both at relatively low levels of memory for the original information (Experiment 1) and at relatively high levels of memory for the original information (Experiment 2). The implications of the present results for interference principles of forgetting are discussed.     

Amalgamations of memories: intrusion of information from one event into reports of another

Numerous researchers have reported that exposure to misleading postevent information (MPI) regarding details in a witnessed event can lead people to report false details from the MPI when asked to report the witnessed event. In such studies, the MPI is presented to participants in the context of information about the witnessed event. This experiment tests the hypothesis that postevent exposure to information that participants know is not about the witnessed event can, nonetheless, affect performance on tests of memory for that event. As predicted, when asked to report details of an event depicted in a slide show, participants tended to intrude details mentioned in a recent postevent narrative that described a different event. © 1998 John Wiley & Sons, Ltd.     

Why misinformation is more likely to be recognised over time: A source monitoring account

Although memory for actual events tends to be forgotten over time, memory for misinformation tends to be retrieved at a stable rate over long delays or at a rate greater than that found immediately after encoding. To examine whether source monitoring errors contribute to this phenomenon, two experiments investigated subjects' memory for the source of misinformation at different retention intervals. Subjects viewed a slide presentation, read a narrative containing misinformation, and, either 10 minutes or 1 week later, completed a recognition test about details seen in the slides and about the source of these details. After the longer retention interval in both experiments, participants were more likely to agree that they had seen misleading information and were also more likely to incorrectly associate the misinformation with the slide event. Theoretical implications of these findings are considered.     

Misleading postevent information and memory for events: arguments and evidence against memory impairment hypotheses

The claim that a person's memory for an event may be altered by information encountered after the event has been influential in shaping current conceptions of memory. The basis for the claim is a series of studies showing that subjects who are given false or misleading information about a previously witnessed event perform more poorly on tests of memory for the event than subjects who are not misled. In this article we argue that the available evidence does not imply that misleading postevent information impairs memory for the original event, because the procedure used in previous studies is inappropriate for assessing effects of misleading information on memory. We then introduce a more appropriate procedure and report six experiments using this procedure. We conclude from the results that misleading postevent information has no effect on memory for the original event. We then review several recent studies that seem to contradict this conclusion, showing that the studies do not pose problems for our position. Finally, we discuss the implications of our conclusions for broader issues concerning memory.     

Memory impairment in the weapon focus effect

Two experiments are reported in which postevent source of misinformation was manipulated within weaponpresent and weapon-absent scenarios. Participants viewed slides depicting either a weapon or a newspaper event and then received either incomplete questioning or a narrative. Both postevent sources contained misleading information about a central and peripheral detail concerning either the weapon or the newspaper scenario. With a modified test in Experiment 1, questioning was found to increase misinformation effects concerning the central item, as compared with a narrative, and more misinformation effects were found for the weapon-peripheral than for the newspaper-peripheral item. In Experiment 2, the participants were more likely to claim to have seen contradictory and additive misinformation about the central item in the slides following questioning, and more contradictory and additive misinformation effects occurred for the weapon-peripheral than for the newspaper-peripheral item. The findings are considered in terms of the effects of both postevent and encoding factors on memory.     

The power of the spoken word: sociolinguistic cues influence the misinformation effect

We investigated whether the sociolinguistic information delivered by spoken, accented postevent narratives would influence the misinformation effect. New Zealand subjects listened to misleading postevent information spoken in either a New Zealand (NZ) or North American (NA) accent. Consistent with earlier research, we found that NA accents were seen as more powerful and more socially attractive. We found that accents per se had no influence on the misinformation effect but sociolinguistic factors did: both power and social attractiveness affected subjects' susceptibility to misleading postevent suggestions. When subjects rated the speaker highly on power, social attractiveness did not matter; they were equally misled. However, when subjects rated the speaker low on power, social attractiveness did matter: subjects who rated the speaker high on social attractiveness were more misled than subjects who rated it lower. There were similar effects for confidence. These results have implications for our understanding of social influences on the misinformation effect.     

How eyewitnesses resist misinformation: Social postwarnings and the monitoring of memory characteristics

Previous findings have been equivocal as to whether the postevent misinformation effect on eyewitness memory is reduced by warnings presented after the misinformation (postwarnings). In the present research, social postwarnings, which characterize the postevent source as a low-credibility individual, diminished the misinformation effect in both cued recall and recognition tests. Discrediting the source as being either untrustworthy or incompetent was effective (Experiment 1). Also, postwarned participants rated reality characteristics of their memories more accurately than did participants receiving no or high-credibility information about the postevent source (Experiment 2). A social postwarning yielded the same results as an explicit source-monitoring appeal and led to longer response times for postevent items, relative to a no-warning condition (Experiments 3 and 4). The findings suggest that the reduced misinformation effect was due to more thorough monitoring of memory characteristics by postwarned participants, rather than to a stricter response criterion or to enhanced event memory.     

Misleading postevent information and working memory capacity: an individual differences approach to eyewitness memory

The present study examines how individual differences in working memory capacity relate to the effect of misleading postevent information on memory for the original event. Participants were shown a film of a crime event and were then asked to unscramble a narrative that included misinformation regarding some of the film's details. Additionally, the working memory capacity of the participants was measured using the operation‐word span task. Finally, in a free recall test, participants recalled fewer correct details in the misinformation condition compared to the control condition. This effect was negatively correlated with working memory capacity. Copyright © 2002 John Wiley & Sons, Ltd.     

Editing misleading information from memory: Evidence for the coexistence of original and postevent information

When misleading postevent information biases one’s memory for an event, what is the fate of the original, accurate information? One possibility is that the new information and the original information coexist in memory, but that the former is simply more accessible. A second hypothesis suggests that the new information replaces the old, and memory is irreversibly altered. Using various retrieval techniques, Loftus and her associates (Greene, Flynn, & Loftus, 1982; Loftus, 1979a, 1979b) have failed repeatedly in attempts to recover original memories after postevent biasing, a finding that supports the alteration hypothesis. In the present study, postevent biasing was demonstrated in two experiments. In each experiment, some subjects were given a warning that the postevent information had included a few inaccurate details. These subjects were able to edit out the inaccurate details and to recover the original facts when the warning came as much as 45 rain after they had read the misleading information, a result that argues for the coexistence of memories. Successful recovery of the original memories was apparently due to the clarity of the warning and to an improved technique for assessing the retrieval of original memories.